Method of and apparatus for making fibrous articles



v. T. PARE 2,384,958

METHOD OF AND APPARATUS FOR MAKING FIBROUS ARTICLES Sept. 18, 1945.

Filed Oct. 14, 1941 3110mm; fidarl'lizrfi u V (lttorneg Patented Sept. 1a, 1945 smmonorsnn mamirns roa memo Us sancass Victor '1'. rue, Collingswood, N. 1, assignor-io America, a corporation of Badio Corporation of I I must 0mm 14. 1041, No. 314m I This invention relates process of and apparatus for forming fibrous articles. such as diaphragms for loudspeakers. and more particularly to the type of articles formed through the process of depositing accreted accumulations of g lemma (cue-set fibrous-material upon perforated forms from a liquid suspension, the present application being a continuation in part of my eopending application Serial No. 181,838, flied August 31, 1937, now Patent No. 2,288,832, granted July '1, 1942.

Heretofore,it has been common practice to mold or felt sound-producing diaphragms of conoid form by the well-known process of causing a layer of fibrous material, such as wood pulp, to become deposited upon the surface of a suitable former. Experience has shown that. aside from various combinations of iibrous material and the additions of various proofing and sizing compounds, accreted layers so formed are all essentially the .sameintexture. Thiscaneasilybeshowntobe the case because of the simple physicallaws inor rag pulp, the material is held in suspension in water and is caused to be drawn by suction through a suitable perforated form. The indi vidual fibres will naturally settle into a similar general arrangement. For more complete information relative to this type of diaphragm and I manufacture, reference is made to Carlisle'; et al., 1,901,631, and Hawley, 1,984,018 and 1,8 2,081.

Bound reproduclng'diaphragms th produced require extensive after-treatment to make them suitable for present day standards of reproduction. This treatment may take the form of calinvention In accordance with my invention, I able to produce a felted layer of accreted fibres that are highly commingled by vibrating, the perforated formerand/or fibres while depositing the fibres from the liquid suspension. -Articles formed in 'this manner are possessed of greater strength and density because the individuaiflbres, previously distorted and disarranged by the heating process, are shifted into.more compact mutual relationship while being drawn into position. In this manner, they also tend to seek a. final posi- 'tion of rest in the accreted layer and a member is thus produced normally free of all stresses.

I have found that a frequency of so cycles, or 120 vibrations,- per secondapplied to the former gives'good results with ordinary pulps, such as ground wood, rag, kraft or sulphite.- However.

the frequency may be varied as the article and pulpdemand. I have chosen the sound-radiatvolved in the process of felting. In aqueous suspensions of beaten fibrous material. such as wood ing diaphragm as an embodiment of my invention. However, itisnot to be limited to said article, as anyone skilled in the art will'readily 5 recognize the fact that it can be advantageously endering, embossing or impregnating with varif ,ous proofing compounds, any or all of which treatments are appliedto the dried member to render it more acceptable as a sound radiator. Because adiaphramsuch as is used in the I conventional type of electrodynamic loudspeaker, is called upontoperforminamannernotusualiy' assoclated'with ordinary paper products, it must possess qualitiesnot generally found in ordinary. P p r.

It is'accordingly an object of my invention to provide a novel acoustic diaphragm of the felted type'that shall have improved acoustic characteristics and greatenstrength.

used in the manufacture of other articles.

' 'I'henovel features that I consider characteristic of my invention are set forth with :particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, as well as additional obiects and advantages thereof, will best be understood from the following description of two embodiments thereof, when read in connection with the accompanying drawing in which Figure l is a sectional view of a perforated formeriior diaphragms showing vibration mechanism constructed in accordance with my present invention,

Figure 2 is a fragmentary sectional view of another arrangement according to my present invention, and I.

Figure 3 is a fragmentary sectional view of a portion of a frusto-conical diaphragm made in accordance with my invention.

' Referring to Fig. l, a casting i of nonferrom A further object of my invention is to provide a new method or process for producingmy improved diaphragm. as well as a novel device for oarryingout the method or process.

Other objects and advantages inherent in my to metal is drilled and grooved at i lover its surface to. provide free passage for the filtrate from the I pulp suspension. .A substantial base plate I of metal is drilled and tapped for an exit pipe I.

The casting i is bolted to the base plate as shown. A strut 8 is secured to the inner surface of the casting former i, as by bolts, the center boss of tbestrutlbcingdrilledandthreadedtoldiuatably receive a soft steel end in of an armature I,

W111 ppear from the following em mY -Drooessanddevice:

preferably built up of laminations at portion lb. A magnetic flux gap is preferably provided at It between the end of the armature and the yoke i i, and is adjustable by means of the screw-threaded connection between armature portion la and the strut I. One or more nuts I. serve to lock the armature in position on the strut. A small clearance is preferably provided at 2i between the armature and upper ends of the yoke.

A solenoid winding structure 0, terminating in the connectors 8, is rigidly mounted within a laminated iron field or yoke ii, in turn clamped in position by a clamp II to the base plain, 2.

A perforated former or screen i is removably placed in position over the former casting i and is provided with small holes throughout its entire surface, some of which are indicated at I. It is upon the screen 3 that the deposited layer of pulp fibre accumulates to form a' diaphragm 22 and from which the diaphragm is removed after being dried.

The complete former is moved downward into the pulp suspension it, contained in a suitable tank II, and a suction connection is made through pipe 4 sliding through the stuffing box II, and thence to a flexible hose ll, which in turn that vibration of the required frequency and am-' plitude can be supplied with any one of several well-known mechanical means.

Again referring to Fig. 1, it is evident that when the coil 3 is energized from a source of (iii-cycle current, a 120-cycle vibration is imparted tothe structure i. The amplitude of the imparted vibration does not need to be excessive in part i and it, in turn, is transferred to the finely perforated-metal screen shown at 3. At the instant that suction is applied through the pipe 4, fibres suspended in the liquid is are drawn to the sur- Iface of part 3, which, because of its violent agitation, causes the fibres to settle down and seek their most natural positions. Because the accretion occurs both by suction and a shifting or shaking process, a superior type of felted product isthus produced.

For improved acoustic fidelity, in certain cases it is preferable to have the smaller base portion of the diaphragm stiffer and denser, as for the better reproduction of higher audio frequencies.

With'the vibration means attached to the former I in the manner shown in Figure 1, the smaller base area will receive a greater amplitude of vibration. The outer portion may be held rigid and maintained free of periodic vibration. The portion of the former l which is subiected to vibrations of greatest amplitude will cause the vice verse.

to make the corrugated periphery portion denser than the adjacent portions. This can readily be accomplished by the arrangement shown in Fig. 2 wherein a bolt 30 couples the strut i substantially casting I may be provided with a peripheral flange 33 to which two or more armatures of suitable vibrating devices may be secured at diametrically opposite sides of, or circumferentially around, the flange 33, only one being shown in Fig. 2 for the sake of simplicity. The arrangement shown in Fig. 2 permits vibrating the peripheral portion of the casting i and the former I locally, while the central portion thereof is maintained substantially stationary. If desired, the central portion may also be vibrated, as in Fig. 1, and this may be'to a greater or lesser extent (that is, with greater or lesser amplitude) than the periphery of the diaphragm.

Although I have shown and described certain specific embodiments of my invention, I am fully aware that many modifications thereof are pos 1. In the process of forming fibrous articles by accretion upon a former in a liquid suspension of flbres, the steps which comprise causing fibres .to be accreted simultaneously on the entire surface of said former, and simultaneously vibrating one portion of said former locally to a greater extent than another portion thereof whereby the fibres accreted on said flrst'named portion are arranged in more compact mutual relationship than are the flbres accreted on said second named Portion.

2. In the process of forming fibrous articles by accretion upon a former in a liquid suspension of flbres, the steps which comprise causing said flbres to be accreted simultaneously on the entire surface of said former, maintaining a portion of said former relatively stationary while accreting flbres on said portion, and simultaneously vibrating 'another portion of said former while accreting fibres on said latter portion whereby the fibres accreted on said latter portion are ar ranged in more compact mutual relationship than are said first namedflbres.

3. In apparatus for. forming fibrous articles by accretionof fibres from a liquid suspension there of, the combination of a tank adapted to receive said liquid, a former within said tank positioned therein to be immersed in said liquid and adapted to have the flbres accreted thereon, and means for simultaneously vibrating one portion of said form:

I er locally to a'greater extent than another por said liquid, a former within said tank positionedtherein to be immersed in said liquid and adapted to have the "fibres accreted thereon, means for vibrating certain portions of said former, and

'rieidlytoabridge an onthebase plate 2. The

Men thereof.

' I 4. In apparatus for forming'fibroiis-artlcles by accretion of flbres from a liquid suspension there of, the combination of a tank adapted to receive means substantially confining certain other por tions thereof against vibration relative to said first named portions.

VICTOR, '1'. rant. 

